node/browser capable module check

nodemodule.js

(function() {
  var Validator = (function() {
    var Validator = function(options) {
      ...
    };

    Validator.prototype.foo = function foo() {
      ...
    };

    return Validator;
  })();

  if (typeof module !== 'undefined' && typeof module.exports !== 'undefined')
    module.exports = Validator;
  else
    window.Validator = Validator;
})();

If a project goes beyond a few script tags, then I think the best alternative is to use browserify instead of script tags.

browserify will create a functioning "local module system" within a javascript file which can bundle all the individual scripts. While there is some overhead to add the local module system into the javascript, it is worth it in terms simplifying deployment and reducing the number of HTTP requests (usually means a faster loading web page).